The present invention relates to image processing apparatus for use in copying machines, facsimile systems or the like for scanning a document on a contact glass plate or like document support table with an optical system while moving the document and the optical system relative to each other to read an image of the document and processing the resulting image signals as required, and more particularly to image processing apparatus adapted to detect the size of documents, modify edge areas of documents and discriminate marked areas on documents.
As disclosed in Unexamined Japanese Patent Publication SHO 61-6636, image processing apparatus adapted to detect the size of documents or perform other processes are known in which the image signals obtained by scanning a document with an optical system are directly stored in memory means temporarily, and the desired process is executed based on the stored signals.
Further Unexamined Japanese Patent Publication SHO 62-2778 discloses an image processing apparatus wherein the image signals obtained by scanning a document on a document support table with an optical system are temporarily stored as they are in memory means, and the position and size of the document on the table are detected from the data obtained by scanning all the addresses of the memory means successively at a specified interval.
The conventional image processing apparatus described above necessitate memory means of great capacity since all the signals representing a document image are to be stored and requires a long period of time for image processing since the memory means also is to be scanned successively.
On the other hand, Unexamined Japanese Patent Publications SHO 55-73041, SHO 57-119380, SHO 59-139486, SHO 62-239662 and SHO 62-239663 propose image processing apparatus adapted to detect image density signals corresponding to the light reflected from a document using a photodetector, discriminate a specified area on the document marked with a marking pen or the like based on the density signals, and process the marked area on the document based on the result of discrimination.
These conventional apparatus include those adapted to discriminate the marked area with use of a color filter on the photodetector to alter the sensitivity level, or with use of a color sensor as the photodetector. With such apparatus, the photodetector or sensor unit is complex in construction and costly. The apparatus disclosed in the publication SHO 62-239662 or SHO 62-239663 is adapted to detect a mark at a specific position on the document and process the image in an area on the document corresponding to this position, so that characters, diagram or the like at an optional position on the document can not be processed. The apparatus of the publication SHO 59-139486 discriminates a marked area on the document simultaneously with the scanning operation of the optical system and is therefore adapted for high-speed processing, whereas the image processing to be performed is limited only to cutout processing. The apparatus further requires a memory of large capacity for storing the mark signals obtained from the document for the entire area of the document.